Angioedema with a normal complement profile except for a borderline low C1q

11/2/2012
I have a 48 y/o nurse with history of two episodes of Uvular edema in the last three months. The only abnormal lab finding is low C1q. Levels at Quest labs 4.6 (N 5.0 – 8.6). Repeated at Labcorp 10.5 (N 11.8 – 24.4). Her other labs include C3, C4, CH50, C1 Inh function and protein, ANA, C1q autoantibody, TSH, Urinalysis, CT neck and CT sinuses. All these labs and X rays are within normal limits. I looked at one of previous answers on this topic. Patient does not have signs of Purpura, Myositis or any other autoimmune disease. I would appreciate any suggestions.

A:

Thank you for your inquiry.

My impression is that your borderline low C1q is not related to your patient’s symptoms, and that she simply has idiopathic angioedema of the uvula. Idiopathic angioedema accounts for the majority of patients who present with uvular edema; however, there are other causes of uvular edema which should be considered. Such cases usually appear only as single case reports, but there is a very small series with a review of the literature which you might find helpful (1). This reference is available to you free of charge online.

The reasons that I feel the C1q is of no clinical importance in her case are the following:
1. As mentioned, it is only borderline low.
2. If it were clinically significantly low, one would expect a low CH50 as well.
3. Low C1q, as you know, has been associated with “autoimmune” diseases, but she has no evidence for such, and I could find no reports of a C1q (in the absence of findings of C1 inhibitor deficiency syndrome) being associated with angioedema per se.

Thank you again for your inquiry and we hope this response is helpful to you.